1. Field of the Invention
The invention relates to electromagnetic flowmeters containing slits to reduce eddy currents and a method of producing the same.
2. Description of the Related Art
Electromagnetic flowmeters have a laminated core and an outer casing made of a magnetically permeable material which is fixed outside the laminated core. In such flowmeters, a recurrent problem exist in the generation of eddy current in the outer casing. As a result, the occurrence of magnetic flux is delayed and large-sized electromagnetic flowmeters are unable to use coils having reduced exciting frequencies.
Another problem which occurs at reduced exciting frequencies is the presence of (1/f) electrochemical noise. In such cases, it becomes difficult to separate the signal-to-noise ratio.
Because of these problems associated with large-sized electromagnetic flowmeters, the laminated core is fixed inside the outer casing and the fixed laminated core is used as the core of the exciting coil. However, when the laminated core is used as the core, eddy currents are generated which reduces efficiency of operation.
One attempt to reduce eddy currents is to cut partial slits in the core. This method is disclosed in Published Examined Japanese Utility Model Application No. 48-44996. One problem with such a method is that the partial slits are cut in the core prior to being fixed to the outer casing. As a result, the core is not firm, and it is difficult to fix the core to the outer casing.
The above-mentioned Japanese application does not disclose an effective method of cutting the slits in the core nor does it disclose how the core is fixed to the outer casing.